NF 270s passing sugar

[tuckermtn]

according to my Hanna digital refractometer, my membranes are passing sugar. Around .2 to .3 This was concentrating to 8-9%, with pressure at 350 and concentrate outflow at 2gpm. My machine has a recirc pump and one 8" and one 4" membrane.

I apologize if this has been covered before, but its late and I am just going to ask. What sort of soultions are there to stop passing this sugar? Is there a wash or rinse treatment, a different method of concentrating, or do I keep all the permeate and run it back through? Or am I looking at a new set of membranes?

Thanks all...

[Bucket Head]

Eric,

I'm new to RO technology, but my membranes are doing about the same as yours. Are yours old? Mine are old- possibly original, so I'm told. I'm going to run these this season and invest in new ones for next year.

Steve

[danno]

I've heard an acid wash (citric acid) will tighten up the membranes and reduce passing sugar. You can buy citric acid at any wine making store, if there's one in your area. Maybe Jerry or someone else who knows more will chime in.

[venus_amos]

Danno, You are right with citric acid. The method is washing as high as possible (104-105 deg f) with the acid, drain membrane and rinse it immediately with very cold permeate. That will tigthen the pores of membrane. But it's a solution temporary. Peoples around here don't use anymore this membrane, because it is deem to pass the sugar.

[802maple]

Danno and Venus are right?

Do your membranes run in series? if they do which one does the concentrate go thru last? It could very well be that one passing the sugar. Is there a simple way of testing the permeate from the individual membranes. If not can you take the second one out of service to see if the machine is still passing sugar. If it is the 4 inch that is passing sugar, you can get one of them reasonable. It doesn't take much .3 sugar loss to pay for one. It only takes 230 gallons to make a gallon of syrup, throw out 1000 gallons of sap in a day and there is 4 and 1/2 gallons of syrup (real money) Besides permeate with sugar in it won't wash the membranes well either.

[sfsshadow]

chech the 0 rings on the membrain.they could be dryed or cracked. some membrains will pass sugar over 8%

[tuckermtn]

I believe they run in series (which I understand means that it goes in one, then in to the other and then finally out)

Chuck (WMF) suggested I get rid of the 4" one right when I got this machine. It looks like the feed goes from out of the pressure pump in to the 4" membrane then out of the 4" and in to the 8". I do not need the higher GPH of having two membranes, so if I'm brave and can figure it out I may re-plumb and unit and pull the 4" out of service. Would love to have a second opinion on how to do it, but Chuck lives and western New York. Jerry you make service calls?

Is the short term acid wash option just a temporary fix?

As to Jerry's numbers- we did over 1000 gals of 2.5% sap yesterday. At $50 per gallon average for syrup, thats close to $250 on the ground. Thats easy math to me. If I need to bite the bullet for new membranes, then thats the answer.

[802maple]

chech the 0 rings on the membrain.they could be dryed or cracked. some membrains will pass sugar over 8%


This is good advice also.

I wish I could but, I am balls to the wall with work right now. Maybe Russ could help you out with some advice also.

[maple connection]

I think you should check the oil ring also, we had that problem on one machine and it was the oil ring. Also try running at about 300 psi and turn you concentrate down so, your around 6% on the concentrate side. See if that helps. The acid wash might help alittle but yes, it is a short term fix.
The NF 270 is made to take off one pass @ 300psi up to about 6 brix. anything more than that and it will start passing sugar. I hope this helped and hope you can fix you problem.

[tuckermtn]

Jerry- I think I saw somewhere you described a way to double check that the permeate had sugar in it? Something about a 20 to 1 reduction?

Thanks-

Eric

[tuckermtn]

maple connection- not sure what you mean by "oil ring"?

I will plan on doing the 300psi and high outflow to see if that helps.

[maple connection]

There is a u cup oil ring on the membrane that folded over. It is on the end of our membrane that seals against the outer canister.

[tuckermtn]

yes I get you now...

thanks-

Eric

[Russell Lampron]

Eric what is the ph of your wash solution? I have heard that you shouldn't wash an NF270 over a ph of 9. I wash mine at a ph of 8 and only get a trace of sugar in my permeate until I get into the teens. Most other membranes are washed at a ph of 11.

I never run mine at over 250psi and recirculate to get it sweet.

[DrTimPerkins]

maple connection- not sure what you mean by "oil ring"?

I will plan on doing the 300psi and high outflow to see if that helps.

I think he means O-ring.

That is very good advice.

What I'd do (in order):

- check the refractometer calibration or double-check with another refractometer. You're very close to the limit of readibility for many units. Could be you're just a tad off on the instrument you're using. The Hannah refractometers are +/1 0.2 Brix, so could be you're calibration is a hair off, or you're not allowing enough time for the temperature to equilibrate. Either of these issues could easily give a reading of 0.2-0.3 Brix when there is actually NO sugar in the permeate.

- Boil down some permeate. Do a 10:1 or 20:1 reduction. That will show you much better whether or not sugar is actually passing.

Once you're absolutely certain it isn't the refractometer and that you are in fact passing sugar....then you can move on to the RO unit itself.

- Check the O-rings on the membrane housing. Some units also have a ceramic O-ring. Check this as well. Warning....it can be a bugger to put these things back together. You may need 2-3 pair of hands.

- As Jerry said, if it's a multi-post unit, try to isolate which membrane is causing the problem.

- Once you rule out everything else, it is likely that you have a leaky membrane. If you can't get an immediate replacement, you could try an acid treatment (most of the equipment dealers have citric acid available). This is only a temporary solution (if it works).

- Replace the membrane.

[danno]

Ditto on checking the refractometer. I thought I was passing sugar again, until I realized snow dripping off my sugarhouse roof was reading .3 sugar as well;). And, no, it was not from my steam condensating on my roof.

I've had to recalibrate the refracto twice already this season - keeps creeping up and down. Ofcourse, turned out that my raw sap was actually 1.5%, not the 2% I was reading.

[sfsshadow]

i used to have a memtic ro like yours.when i had touble with the 4" membrain,i just took it out. didnt have to replum anything. the 0 rings i was refering to, earlier,were the small ones on the coupler and end cap. good luck

[tuckermtn]

Paul- I think I have your old memtek....but I could have you mistaken for someone else.

I did remove the 4" membrane, re plumbed it- pretty easy actually. When it was up and running later on had the same through-put as it did when I had the 4" in the machine.

Took apart the 8" membrane housing, and cleaned all the o-ring surfaces, etc. Upon the suggestion of Joe from Atlantic RO (get this, the guy answers his phone on Sunday. Even called me back later in the day- all on a sunday!) I put some teflon tape around the o-rings on the coupler where it goes in to the membrane and in to the end cap. I think in the off season I am going to have someone machine me some new end caps as mine are showing their age (the machine is 29 yrs old)- pretty pitted and oxidized surfaces.

Ran some sap through it tonight and the permeate coming out tested the same as the poland springs bottled water I had on hand. Was running it at around 300-310psi and letting out around 1.5 gpm.

So I think I have a better handle on it now. Thanks to all who responded. Gotta love the trader....where is the button for sending in a donation...

cheers-

Eric

[802maple]

It looks like you have things under control now.

[danno]

Hey Eric - good to hear.

Joe sells new membrane end caps for older vessels as well. He has a bunch of adapters so we can use new membranes in old vessels. I changed out 20 year old osmonics this year and he had the adapters in stock. I believe he also fabricates if he comes across one that has not yet been made.

[tuckermtn]

Joe has been a wealth of knowledge. What an excellent resource and he takes the time to explain things very well and clearly...thinking about one of the XLE membranes for next season to concentrate up to 10% range.